Vehicle power supply apparatus

ABSTRACT

A vehicle power supply apparatus includes first and second device batteries, a power supply line, and a current path. The power supply line includes first, second, and third segments. The first segment is coupled between a first end of the power supply line and a first diode. The second segment is coupled between the first diode and a first switch. The third segment is coupled between the first switch and a second end of the power supply line. The current path is routed from the third segment to the first segment through a second diode, to bypass the second segment. An electric device of a vehicle is coupled to the first segment. The second device battery is coupled to the second segment. The first device battery is coupled to the third segment through a second switch.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from Japanese Patent Application No.2019-097615 filed on May 24, 2019, the entire contents of which arehereby incorporated by reference.

BACKGROUND

The technology relates to a vehicle power supply apparatus that supplieselectric power to an electric device of a vehicle.

In recent years, some vehicles include a plurality of device batteriesand are able to supply electric power from any one of the devicebatteries to an electric device of the vehicle. Examples of the electricdevice of the vehicle may include, without limitation, auxiliaries thatcontribute to travel of the vehicle. The device batteries are, forexample, 12-volt accumulators. In engine vehicles, the device batteriesare also called batteries for auxiliaries.

Japanese Unexamined Patent Application Publication (JP-A) No.2018-198519 describes a vehicle including a first accumulator and asecond accumulator. The first accumulator and the second accumulatorsupply electric power to an electric motor coupled to an engine. Thevehicle of JP-A No. 2018-198519 is provided with a power supplyapparatus including two switches. One switch is able to isolate theelectric motor and the first accumulator from each other. The otherswitch is able to isolate the electric motor and the second accumulatorfrom each other.

SUMMARY

An aspect of the technology provides a vehicle power supply apparatusincluding a first device battery, a second device battery, a powersupply line, and a current path. The first device battery and the seconddevice battery are configured to supply electric power to an electricdevice of a vehicle. The power supply line includes a first end and asecond end between which a first switch and a first diode areinterposed. The first diode is directed to make a current flow from thefirst switch. The power supply line includes a first segment, a secondsegment, and a third segment. The first segment is coupled between thefirst end and the first diode. The second segment is coupled between thefirst diode and the first switch. The third segment is coupled betweenthe first switch and the second end. The current path is routed from thethird segment to the first segment through a second diode, to bypass thesecond segment. The second diode is directed to make a current flowtoward the first segment. The electric device is coupled to the firstsegment. The second device battery is coupled to the second segment. Thefirst device battery is coupled to the third segment through a secondswitch.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the disclosure, and are incorporated in and constitutea part of this specification. The drawings illustrate embodiments and,together with the specification, serve to explain the principles of thedisclosure.

FIG. 1 is a configuration diagram of a main part of a vehicle on which avehicle power supply apparatus according to one embodiment of thetechnology is mounted.

FIG. 2 is a configuration diagram of a current flow on vehicle travel.

FIG. 3 is a configuration diagram of a current flow during a vehiclestop.

FIG. 4 is a configuration diagram of a current flow at an enginerestart.

FIG. 5 is a configuration diagram of a state with a second devicebattery failing.

FIG. 6 is a configuration diagram of a state with a first device batteryfailing.

FIG. 7 is a configuration diagram of a state in a system halt.

DETAILED DESCRIPTION

In a vehicle including two device batteries, even in a case with one ofthe two device batteries failing, an electric device such as auxiliariesis driven with electric power from the other of the two devicebatteries, making it possible for the vehicle to keep on traveling. Thissometimes results in continuous use of the vehicle, with the failingdevice battery out of repair or replacement.

With the failing device battery left coupled to a power supply line,currents flow into the failing device battery from a normal devicebattery when a system of the vehicle is in operation or in a halt.Moreover, there is possibility of a current flow into the failing devicebattery from a generator or a DC/DC converter when the system of thevehicle is in operation. Accordingly, in the case with the devicebattery failing, it is desirable to isolate the failing device batteryfrom the power supply line both when the system of the vehicle is inoperation and when the system of the vehicle is in the halt. A furtherconsideration is directed to a configuration in which a device batteryis coupled to a power supply line through a switch such as a relay and asemiconductor switch.

In the configuration in which the device battery is coupled to the powersupply line through the switch, controlling the switch makes it possibleto isolate the failing device battery from the power supply line whenthe system of the vehicle is in operation. On the other hand, such aswitch control is unavailable when the system of the vehicle is in thehalt. In this case, a switch that opens uncontrolled is adopted in orderto isolate the failing device battery from the power supply line. But ina case with a configuration in which two device batteries are coupled toa power supply line through their respective switches that openuncontrolled, the device batteries are both isolated from the powersupply line when the system of the vehicle is in the halt. This inhibitsthe power supply line from being supplied with a power supply voltage orelectric power for start-up of the system of the vehicle, rendering thesystem of the vehicle unable to start up.

It is desirable to provide a vehicle power supply apparatus that makesit possible to suppress charge and discharge of whichever of a firstdevice battery and a second device battery has failed, regardless ofwhether a system of a vehicle is in operation or whether the system ofthe vehicle is in a halt. It is desirable to provide a vehicle powersupply apparatus that makes it possible to start up the system of thevehicle from the halt with electric power from whichever device batteryis normal.

In the following, some preferred but non-limiting embodiments of thetechnology are described in detail with reference to the accompanyingdrawings. Note that the following description is directed toillustrative examples of the disclosure and not to be construed aslimiting to the technology. In each of the drawings referred to in thefollowing description, elements have different scales in order toillustrate the respective elements with sizes recognizable in thedrawings. Therefore, factors including, without limitation, the numberof each of the elements, the shape of each of the elements, a size ofeach of the elements, a dimension of each of the elements, a material ofeach of the elements, a ratio between the elements, relative positionalrelationship between the elements, and any other specific numericalvalue are illustrative only and not to be construed as limiting to thetechnology. Further, elements in the following example embodiments whichare not recited in a most-generic independent claim of the disclosureare optional and may be provided on an as-needed basis. Throughout thespecification and the drawings, elements having substantially the samefunction and configuration are denoted with the same referencecharacters to avoid redundant description, and elements not in directrelation to the technology may not be illustrated. FIG. 1 is aconfiguration diagram of a main part of a vehicle on which a vehiclepower supply apparatus according to one embodiment of the technology ismounted.

A vehicle 1 according to an embodiment of the technology may be anengine vehicle, and include an engine 16, drive wheels 18, a clutch 17,and a starter generator 13. The clutch 17 may intermit powertransmission from the engine 16 to the drive wheels 18. The startergenerator 13 may perform power generation and cause a restart of theengine 16.

The vehicle 1 may further include an electric device 11, a first devicebattery 21, a second device battery 22, a power supply line LB, and acurrent path LC. The electric device 11 may include auxiliaries. Thepower supply line LB is provided for transmission of electric power tobe supplied to the electric device 11. The current path LC is able tobypass a current from one end, i.e., a first end, of the power supplyline LB to the other end, i.e., a second end, of the power supply lineLB.

The vehicle 1 may further include a diode D1, a first switch SW1, adiode D2, and a second switch SW2. The diode D1 and the first switch SW1are provided on the power supply line LB. The diode D2 is provided onthe current path LC. The second switch SW2 is interposed between thefirst device battery 21 and the power supply line LB.

In one embodiment of the technology, the diode D1 may serve as a “firstdiode”. In one embodiment of the technology, the diode D2 may serve as a“second diode”. In one embodiment of the technology, the startergenerator 13 may serve as a “power supply device” and a “starter”.

A configuration including the following constituent elements may serveas a vehicle power supply apparatus 2 according to one embodiment of thetechnology: the starter generator 13, the first device battery 21, thesecond device battery 22, the power supply line LB including the diodeD1 thereon, the current path LC including the diode D2 thereon, thefirst switch SW1, the second switch SW2, and a controller 12. Asmentioned above, the starter generator 13 may serve as the “power supplydevice” according to one embodiment of the technology.

The electric device 11 may include an electrically-powered device thatcontributes to travel of the vehicle 1. Non-limiting examples of theelectric device 11 may include auxiliaries that provide assistance withdriving of the engine 16. The electric device 11 may include anundepicted regulator circuit and the controller 12. The regulatorcircuit may step down a power supply voltage of the power supply line LBto generate a power supply voltage for a control system. The powersupply voltage for the control system may be, for example, 5 V. Thecontroller 12 may operate with the voltage of the regulator circuit.

The controller 12 may perform a control of the vehicle 1. The control ofthe vehicle 1 may include a travel control and a system control of thevehicle 1. In one specific but non-limiting example, the controller 12may perform an opening and closing control of the first switch SW1 andthe second switch SW2, a control of engagement and disengagement of theclutch 17, an operation control of the starter generator 13, and anoperation control of the electric device 11 inclusive of theauxiliaries. The controller 12 may include a single electronic controlunit (ECU), or alternatively, the controller 12 may include a pluralityof ECUs that cooperate in association by communication.

The first device battery 21 may include, for example, a lithium ionsecondary battery, and output, for example, a 12-volt power supplyvoltage for devices. The second device battery 22 may include, forexample, a lead accumulator, and output a power supply voltage that issubstantially the same as that of the first device battery 21. It is tobe noted that there is no particular limitation on kinds or categoriesof the first device battery 21 and the second device battery 22. Thefirst device battery 21 may be of a different kind from what isdescribed above, e.g., a lead accumulator or a nickel hydrogen secondarybattery. The second device battery 22 may be of a different kind fromwhat is described above, e.g., a lithium ion secondary battery or anickel hydrogen secondary battery. The first device battery 21 and thesecond device battery 22 may be accumulators of the same kind, oralternatively, the first device battery 21 and the second device battery22 may be accumulators of different kinds.

The starter generator 13 may utilize part of motive power of the engine16 in the driving of the engine 16, to perform power generation. Thestarter generator 13 may supply electric power thus generated, to thepower supply line LB. The starter generator 13 may output, to the powersupply line LB, a slightly higher voltage than an output voltage of thefirst device battery 21 and an output voltage of the second devicebattery 22. Thus, the starter generator 13 is able to supply a chargecurrent to the first device battery 21 and the second device battery 22,and to supply a drive current to the electric device 11. The startergenerator 13 may also operate as an electric motor. For example, in acase where the engine 16 is stopped and heated, the starter generator 13is able to give motive power to the engine 16, to cause a restart of theengine 16. The starter generator 13 may be divided into a generator anda starter.

The power supply line LB may be a power line from which, for example,the 12-volt power supply voltage for the devices is outputted. The powersupply line LB includes one end, i.e., the first end, and the other end,i.e., the second end, between which the diode D1 and the first switchSW1 are provided. The power supply line LB includes a first segment S 1,a second segment S2, and a third segment S3. The first segment S1 iscoupled between the first end and the diode D1. The second segment S2 iscoupled between the diode D1 and the first switch SW1. The third segmentS3 is coupled between the first switch SW1 and the second end. Theelectric device 11 is coupled to the first segment S1. The second devicebattery 22 is coupled to the second segment S2. The first device battery21 is coupled to the third segment S3 through the second switch SW2. Thestarter generator 13 may be coupled to the third segment S3.

The diode D1 on the power supply line LB is directed to make a currentflow from the first switch SW1. For example, the diode D1 may bedirected to make a current flow from the first switch SW1 toward thefirst segment S1. That is, a cathode of the diode D1 is coupled to thefirst segment S1, and an anode of the diode D1 is coupled to the secondsegment S2.

The current path LC may include one end coupled to the first segment S1of the power supply line LB, and another end coupled to the thirdsegment S3 of the power supply line LB. Hence, it is possible for thecurrent path LC to make a current flow from the third segment S3 to thefirst segment S 1, to bypass the second segment S2. The diode D2 isprovided between the two ends of the current path LC. The diode D2 isdirected to make a current flow toward the first segment S1. That is, acathode of the diode D2 is coupled to the first segment S1 of the powersupply line LB, and an anode of the diode D2 is coupled to the thirdsegment S3 of the power supply line LB.

The first switch SW1 may include a switch that opens uncontrolled, i.e.,a normally open switch. The first switch SW1 may include, for example, arelay, but the first switch SW1 may include a semiconductor switch. Arelay that opens uncontrolled corresponds to a configuration that opensunenergized. A semiconductor switch that opens uncontrolled correspondsto a configuration that opens when an output to a control terminal is ata ground potential.

The second switch SW2 may include a switch that closes uncontrolled,i.e., a normally close switch. The second switch SW2 may include, forexample, a relay, but the second switch SW2 may include a semiconductorswitch. A relay that closes uncontrolled corresponds to a configurationthat closes unenergized. A semiconductor switch that closes uncontrolledcorresponds to a configuration that closes when an output to a controlterminal is at a ground potential.

<Description of Operation>

FIG. 2 is a configuration diagram of a current flow on vehicle travel.On the travel of the vehicle 1, the engine 16 operates, and its motivepower is transmitted to the drive wheels 18. Meanwhile, part of themotive power of the engine 16 is transmitted to the starter generator13, causing the starter generator 13 to perform the power generation. Ina case where the first device battery 21 and the second device battery22 are normal, the first switch SW1 and the second switch SW2 are keptin a closed state, by the control by the controller 12. Accordingly, asillustrated in FIG. 2, electric power generated by the starter generator13 is transmitted to the first device battery 21, the second devicebattery 22, and the electric device 11 through the power supply line LB.

FIG. 3 is a configuration diagram of a current flow during a vehiclestop. When the engine 16 stops while the system of the vehicle 1 is inoperation, the power generation by the starter generator 13 stops. Inthe case where the first device battery 21 and the second device battery22 are normal, the first switch SW1 and the second switch SW2 are keptin the closed state. Thus, electric power is supplied to the electricdevice 11 from whichever of the first device battery 21 and the seconddevice battery 22 has a higher output voltage. For example, in a casewhere an output voltage of the second device battery 22 is slightlyhigher, electric power is supplied to the electric device 11 from thesecond device battery 22 through the power supply line LB, asillustrated in FIG. 3. Electric power thus supplied allows the electricdevice 11 including the controller 12 to operate, to maintain theoperation of the system of the vehicle 1.

FIG. 4 is a configuration diagram of a current flow at an enginerestart. Here is assumed a case where the engine 16 temporarily stopsbecause of a temporary stop of the vehicle 1, and thereafter, the engine16 is restarted to allow the vehicle 1 to travel again. It is, however,assumed that the first device battery 21 and the second device battery22 are normal. In this case, the controller 12 switches the first switchSW1 to an open state and disengages the clutch 17. In this state, thecontroller 12 allows the starter generator 13 to operate as an electricmotor for the restart of the engine 16. The presence of the first switchSW1 in the open state and the diode D2 inhibits a current from flowingfrom the second device battery 22 toward the starter generator 13. Thus,the starter generator 13 operates solely with electric power from thefirst device battery 21. Because the starter generator 13 has relativelygreat power consumption, there occurs a great voltage drop in the thirdsegment S3 of the power supply line LB. But the first switch SW1 beingopen keeps the voltage drop in the third segment S3 from extending tothe first segment S1 and the second segment S2. Hence, it is possible toreduce possibility that the power supply voltage supplied to theelectric device 11 becomes lower than a lower limit voltage thatmaintains the operation of the electric device 11.

<Case with Second Device Battery Failing>

FIG. 5 is a configuration diagram of a state with the second devicebattery failing. In a case where the second device battery 22 hasfailed, while the system of the vehicle 1 is in operation, thecontroller 12 continues a control of opening the first switch SW1 andclosing the second switch SW2. Such a control state of the first switchSW1 and the second switch SW2 is referred to as a “control with thesecond device battery 22 failing”.

As illustrated in FIG. 5, in the control with the second device battery22 failing, the starter generator 13 performs the power generation onthe travel of the vehicle 1, and electric power thus generated issupplied to the first device battery 21 through the third segment S3 ofthe power supply line LB, to charge the first device battery 21.Furthermore, electric power generated is supplied to the electric device11 through the current path LC, to allow the electric device 11 tooperate. The output voltage of the second device battery 22 lowersbecause of the failure, causing the voltage of the second segment S2 tobecome lower than the voltage of the first segment S1 of the powersupply line LB. Thus, the presence of the diode D1 prevents the failingsecond device battery 22 from discharging. Moreover, the diode D1 andthe first switch SW1 in the open state prevent a current from flowinginto the second segment S2 of the power supply line LB. This prevents acurrent from flowing into the failing second device battery 22.

In the control with the second device battery 22 failing, during thestop of the engine 16, electric power is supplied to the electric device11 from the first device battery 21 through the current path LC. Thisallows the electric device 11 including the controller 12 to operate,maintaining the operation of the system of the vehicle 1. At thisoccasion, the output voltage of the second device battery 22 lowersbecause of the failure, and the diode D1 acts to cut off the powersupply line LB. This prevents the second device battery 22 fromdischarging, while preventing a current from flowing into the seconddevice battery 22.

Description now moves on to a case where the system of the vehicle 1 isin operation, with the first device battery 21 and the second devicebattery 22 having been normal, and with both the first switch SW1 andthe second switch SW2 kept in the closed state, and then, the seconddevice battery 22 fails. In this case, with the first switch SW1 and thesecond switch SW2 in the closed state, a current of the power supplyline LB is drawn into the failing second device battery 22. This maycause the power supply voltage of the power supply line LB to lower evenif the first device battery 21 is normal. In a case where the powersupply voltage of the power supply line LB becomes lower than a lowerlimit voltage that makes it possible to maintain the control of thefirst switch SW1 and the second switch SW2, the first switch SW1automatically switches to the open state. This stops the current frombeing drawn into the failing second device battery 22, allowing anoutput of the normal first device battery 21 to restore the power supplyvoltage of the third segment S3 and the first segment S1 of the powersupply line LB. Hence, it is possible to allow the electric device 11including the controller 12 to operate, maintaining the operation of thesystem of the vehicle 1.

<Case with First Device Battery Failing>

FIG. 6 is a configuration diagram of a state with the first devicebattery failing. In a case where the first device battery 21 has failed,while the system of the vehicle 1 is in operation, the controller 12maintains a control of closing the first switch SW1 and opening thesecond switch SW2. Such a control state of the first switch SW1 and thesecond switch SW2 is referred to as a “control with the first devicebattery 21 failing”.

As illustrated in FIG. 6, in the control with the first device battery21 failing, the starter generator 13 performs the power generation onthe travel of the vehicle 1, and electric power thus generated issupplied to the second device battery 22 through the power supply lineLB, to charge the second device battery 22. Furthermore, electric powergenerated is supplied to the electric device 11 through the power supplyline LB, allowing the electric device 11 to operate. Because the failingfirst device battery 21 is isolated from the power supply line LB, thefailing first device battery 21 neither discharges nor has any currentflowing therein.

In one alternative, in a state illustrated in FIG. 6, electric power maybe transmitted to the first segment S1 from the third segment S3 of thepower supply line LB through the current path LC and the diode D2.

In the control with the first device battery 21 failing, during the stopof the engine 16, electric power is supplied to the electric device 11from the second device battery 22 through the power supply line LB. Thisallows the electric device 11 including the controller 12 to operate,maintaining the operation of the system of the vehicle 1. Because thefailing first device battery 21 is isolated from the power supply lineLB, the failing first device battery 21 neither discharges nor has anycurrent flowing therein.

<In System Halt>

FIG. 7 is a configuration diagram of a state in a system halt. In thesystem halt, the controller 12 keep from controlling the first switchSW1 and the second switch SW2, or alternatively, the first switch SW1and the second switch SW2 are not energized for the control.Accordingly, the first switch SW1, being normally open, is brought tothe open state, and the second switch SW2, being normally closed, isbrought to the closed state.

In the case where both the first device battery 21 and the second devicebattery 22 are normal, in the system halt, as illustrated in FIG. 7, theelectric device 11 is supplied with the power supply voltage fromwhichever has the higher output voltage. In other words, the seconddevice battery 22 is available for outputting the power supply voltageto the electric device 11 through the power supply line LB. The firstdevice battery 21 is available for outputting the power supply voltageto the electric device 11 through the current path LC. The power supplyvoltage allows the controller 12 to perform standby operation. Thismakes it possible for the controller 12 to operate to start up thesystem of the vehicle 1, upon an operation by an occupant for thestart-up of the system of the vehicle 1.

In the system halt, in a case where the first device battery 21 hasfailed and the second device battery 22 is normal, the output voltage ofthe failing first device battery 21 lowers. This causes a cut-off actionof the diode D2, preventing a current from flowing through the currentpath LC. Moreover, in the system halt, the starter generator 13 does notoperate. Accordingly, the failing first device battery 21 neitherdischarges nor has any current flowing therein.

Meanwhile, even if the first device battery 21 has failed, the powersupply voltage is supplied to the electric device 11 from the seconddevice battery 22 through the power supply line LB. The power supplyvoltage allows the controller 12 to perform the standby operation. Thismakes it possible for the controller 12 to operate to start up thesystem of the vehicle 1, upon the operation by the occupant for thestart-up of the system of the vehicle 1.

In the system halt, in a case where the first device battery 21 isnormal and the second device battery 22 has failed, the output voltageof the failing second device battery 22 lowers. Thus, in the systemhalt, owing to a cut-off action of the diode D1 and the first switch SW1in the open state, no current flows between the first segment S1 and thesecond segment S2 of the power supply line LB, and between the thirdsegment S3 and the second segment S2 of the power supply line LB.Accordingly, the failing second device battery 22 neither discharges norhas any current flowing therein.

Meanwhile, even if the second device battery 22 has failed, the powersupply voltage is supplied to the electric device 11 from the firstdevice battery 21 through the current path LC. The power supply voltageallows the controller 12 to perform the standby operation. This makes itpossible for the controller 12 to operate to start up the system of thevehicle 1, upon the operation by the occupant for the start-up of thesystem of the vehicle 1.

<Failure Diagnosis>

In the vehicle 1 including the vehicle power supply apparatus 2according to this embodiment mounted thereon, a failure diagnosis of thefirst device battery 21 and the second device battery 22 may be made,for example, as follows.

In the failure diagnosis of the second device battery 22, the controller12 may measure the voltage of the first segment S1 of the power supplyline LB, with the first switch SW1 switched to the open state. In a casewhere a measured value is equal to or smaller than a predeterminedthreshold voltage, the controller 12 may determine that the seconddevice battery 22 has failed. In another alternative, the controller 12may be configured to measure a current of the second device battery 22,to determine that the second device battery 22 has failed, in a casewhere a measured value of the charge current of the second devicebattery 22 is abnormal. The failure diagnosis based on the currentmeasurement is able to be executed, with the first switch SW1 kept inthe closed state. Hence, it is possible for the controller 12 to makethe failure diagnosis highly frequently.

In the failure diagnosis of the first device battery 21, the controller12 may measure the output voltage of the first device battery 21, withthe second switch SW2 switched to the open state. In a case where ameasured value is equal to or smaller than a predetermined thresholdvoltage, the controller 12 may determine that the first device battery21 has failed. In another alternative, the controller 12 may beconfigured to measure a current of the first device battery 21, todetermine that the first device battery 21 has failed, in a case where ameasured value of the charge current of the first device battery 21 isabnormal. The failure diagnosis based on the current measurement is ableto be executed, with the second switch SW2 kept in the closed state.Hence, it is possible for the controller 12 to make the failurediagnosis highly frequently.

As described, according to the vehicle power supply apparatus 2 of thisembodiment, the power supply line LB is divided into the first segmentS1, the second segment S2, and the third segment S3 by the diode D1 andthe first switch SW1. Moreover, the first device battery 21 is coupledto the third segment S3 through the second switch SW2. The second devicebattery 22 is coupled to the second segment S2. Furthermore, theelectric device 11 is coupled to the first segment S1. With thisconfiguration, opening the first switch SW1 and closing the secondswitch SW2 makes it possible to supply electric power to the electricdevice 11 from the first device battery 21 or the second device battery22, while preventing the current flow into the second device battery 22from the first device battery 21 and preventing the current flow intothe first device battery 21 from the second device battery 22.Accordingly, in the system halt of the vehicle 1, switching the firstswitch SW1 and the second switch SW2 as described above makes itpossible to isolate whichever of the first device battery 21 and thesecond device battery 22 has failed, and to start up the system of thevehicle 1 with whichever device battery is normal.

Moreover, according to the vehicle power supply apparatus 2 of thisembodiment, the starter generator 13 may be coupled to the third segmentS3 of the power supply line LB. Accordingly, when the starter generator13 performs the power generation while the system of the vehicle 1 is inoperation, it is possible to transmit electric power thus generated tothe first device battery 21, the second device battery 22, and theelectric device 11, and to use electric power generated for the chargingof the first device battery 21 and the second device battery 22 and forthe operation of the electric device 11. Moreover, in the case where thefirst device battery 21 or the second device battery 22 has failed,switching the first switch SW1 or the second switch SW2 makes itpossible to isolate solely whichever device battery has failed, and touse electric power generated for the charging of whichever devicebattery is normal and for the operation of the electric device 11.

Furthermore, according to the vehicle power supply apparatus 2 of thisembodiment, the first switch SW1 may include a normally open switch, andthe second switch SW2 may include a normally closed switch. Accordingly,in the system halt of the vehicle 1, the control of the first switch SW1and the second switch SW2 is automatically terminated, making itpossible to open the first switch SW1 and to close the second switchSW2. Hence, a transition of the vehicle 1 to the system halt allows foran automatic transition to the system halt that makes it possible tocope with whichever of the first device battery 21 and the second devicebattery 22 has failed.

In addition, according to the vehicle power supply apparatus 2 of thisembodiment, the controller 12 may control the first switch SW1 and thesecond switch SW2. The controller 12 may be configured to operate withelectric power transmitted to the first segment S1 of the power supplyline LB. With this configuration, it is possible to allow the controller12 to use electric power supplied through a similar route to those forother ECUs. It is, therefore, unnecessary to provide a route forelectric power transmission dedicated to the controller 12. In such aconfiguration, in the system halt of the vehicle 1, interruption of thepower supply voltage of the power supply line LB may render it unable tostart up the vehicle 1. However, with the forgoing configuration,electric power supply is provided from the first device battery 21 orthe second device battery 22. It is, therefore, possible to suppress thevehicle 1 from being unable to start up, insofar as either the firstdevice battery 21 or the second device battery 22 is normal.

Furthermore, according to the vehicle power supply apparatus 2 of thisembodiment, in the case where the second device battery 22 is foundfailing, the controller 12 may open the first switch SW1 and close thesecond switch SW2, while the system of the vehicle 1 is in operation.Refer to FIG. 5. Hence, it is possible to isolate the failing seconddevice battery 22 from the system, and supply electric power to theelectric device 11 from the normal first device battery 21.

In addition, according to the vehicle power supply apparatus 2 of thisembodiment, the third segment S3 of the power supply line LB may becoupled to the starter generator 13 that serves as the starter. Thecontroller 12 may open the first switch SW1 at the start of the engine16. With such a control, it is possible to prevent the considerablevoltage drop in the third segment S3 of the power supply line LB fromextending to the electric device 11. The voltage drop is caused by thegreat power consumption of the starter generator 13 at the start of theengine 16.

Although some preferred embodiments of the technology are describedabove by way of example with reference to the accompanying drawings, thetechnology is by no means limited to the embodiments described above.For example, in the forgoing example embodiments, description is givenof the case where the vehicle 1 is an engine vehicle. However, thevehicle 1 may be, for example, an electric vehicle (EV) or a hybridelectric vehicle (HEV). In the case where the vehicle 1 is, for example,an EV or an HEV, not only the generator but also a DC/DC converter mayserve as the power supply device configured to supply electric power tothe power supply line LB. The DC/DC converter is configured to step downa voltage from a main battery of a high voltage and to output thestepped-down voltage. The main battery may accumulate electric power fortraveling.

Moreover, in the forgoing example embodiments, the first diode accordingto one embodiment of the technology is exemplified by the diode D1,i.e., a device dedicated to rectification. Instead, for example, aparasitic diode included in a normally open semiconductor switch mayserve as the first diode according to one embodiment of the technology.With this configuration, the semiconductor switch may be controlled toturn on, in a period when it is known that a current flows to a firstsegment, e.g., the first segment S1, from a second segment, e.g., thesecond segment S2, of a power supply line, e.g., the power supply lineLB. This makes it possible to reduce power loss generated in the firstdiode, leading to improved fuel efficiency of the vehicle.

Similarly, in the forgoing example embodiments, the second diodeaccording to one embodiment of the technology is exemplified by thediode D2, i.e., a device dedicated to rectification. Instead, forexample, a parasitic diode included in a normally open semiconductorswitch may serve as the second diode according to one embodiment of thetechnology. With this configuration, the semiconductor switch may becontrolled to turn on, in a period when it is known that a current flowsto a first segment, e.g., the first segment S1, from a third segment,e.g., the third segment S3, through a current path, e.g., the currentpath LC. This makes it possible to reduce power loss generated in thesecond diode, leading to improved fuel efficiency of the vehicle.

In addition, the details described in the forgoing example embodimentsmay be appropriately changed insofar as the changes fall within a rangenot departing from the scope of the technology.

The controller 12 illustrated in FIG. 1 is implementable by circuitryincluding at least one semiconductor integrated circuit such as at leastone processor (e.g., a central processing unit (CPU)), at least oneapplication specific integrated circuit (ASIC), and/or at least onefield programmable gate array (FPGA). At least one processor isconfigurable, by reading instructions from at least one machine readablenon-transitory tangible medium, to perform all or a part of functions ofthe controller 12. Such a medium may take many forms, including, but notlimited to, any type of magnetic medium such as a hard disk, any type ofoptical medium such as a CD and a DVD, any type of semiconductor memory(i.e., semiconductor circuit) such as a volatile memory and anon-volatile memory. The volatile memory may include a DRAM and a SRAM,and the nonvolatile memory may include a ROM and a NVRAM. The ASIC is anintegrated circuit (IC) customized to perform, and the FPGA is anintegrated circuit designed to be configured after manufacturing inorder to perform, all or a part of the functions of the controller 12illustrated in FIG. 1.

It should be appreciated that modifications and alterations may be madeby persons skilled in the art without departing from the scope asdefined by the appended claims. The use of the terms first, second, etc.does not denote any order or importance, but rather the terms first,second, etc. are used to distinguish one element from another. Thetechnology is intended to include such modifications and alterations inso far as they fall within the scope of the appended claims or theequivalents thereof.

The invention claimed is:
 1. A vehicle power supply apparatus,comprising: a first device battery and a second device batteryconfigured to supply electric power to an electric device of a vehicle;a power supply line including a first end and a second end between whicha first switch and a first diode are interposed, the first diode beingdirected to make a current flow from the first switch, the power supplyline including a first segment, a second segment, and a third segment,the first segment being coupled between the first end and the firstdiode, the second segment being coupled between the first diode and thefirst switch, and the third segment being coupled between the firstswitch and the second end; and a current path routed from the thirdsegment to the first segment through a second diode, to bypass thesecond segment, the second diode being directed to make a current flowtoward the first segment, the electric device being coupled to the firstsegment, the second device battery being coupled to the second segment,and the first device battery being coupled to the third segment througha second switch.
 2. The vehicle power supply apparatus according toclaim 1, further comprising a power supply device that is able to supplycharging electric power to the first device battery and the seconddevice battery, wherein the power supply device is coupled to the thirdsegment.
 3. The vehicle power supply apparatus according to claim 2,wherein the first switch comprises a switch that opens uncontrolled, andthe second switch comprises a switch that closes uncontrolled.
 4. Thevehicle power supply apparatus according to claim 3, further comprisinga controller configured to control the first switch and the secondswitch, wherein the controller operates with electric power transmittedto the first segment of the power supply line.
 5. The vehicle powersupply apparatus according to claim 4, wherein on a condition that thesecond device battery is found failing, the controller opens the firstswitch and closes the second switch while a system of the vehicle is inoperation.
 6. The vehicle power supply apparatus according to claim 2,further comprising a controller configured to control the first switchand the second switch, wherein the controller operates with electricpower transmitted to the first segment of the power supply line.
 7. Thevehicle power supply apparatus according to claim 6, wherein on acondition that the second device battery is found failing, thecontroller opens the first switch and closes the seond switch while asystem of the vehicle is in operation.
 8. The vehicle power supplyapparatus according to claim 7, wherein the third segment of the pwersupply line is coupled to a starter configured to cause a restart of anengine of the vehicle, and the controller opens the first switch whilethe starter is driven.
 9. The vehicle power supply apparatus accordingto claim 6, wherein the third segment of the power supply line iscoupled to a starter configured to cause a restart of an engine of thevehicle, and the controller opens the first switch while the starter isdriven.
 10. The vehicle power supply apparatus according to claim 1,wherein the first switch comprises a switch that opens uncontrolled, andthe second switch comprises a switch that closes uncontrolled.
 11. Thevehicle power supply apparatus according to claim 10, further conprisinga controller configured to control the first switch and the secondswitch, wherein the controller operates with electric power transmittedto the first segment of the power supply line.
 12. The vehicle powersupply apparatus according to claim 11, wherein on a condition that thesecond device battery is found failing, the controller opens the firstswitch and closes the second switch while a system of the vehicle is inoperation.
 13. The vehicle power supply apparatus according to claim 1,further comprising a controller configured to control the first switchand the second switch, wherein the controller operates with electricpower transmitted to the first segment of the power supply line.
 14. Thevehicle power supply apparatus according to claim 13, wherein on acondition that the second device battery is found failing, thecontroller opens the first switch and closes the second switch while asystem of the vehicle is in operation.
 15. The vehicle power supplyapparatus according to claim 14, wherein the third segment of the powersupply line is coupled to a starter configured to cause a restart of anengine of the vehicle, and the controller opens the first switch whilethe starter is driven.
 16. The vehicle power supply apparatus accordingto claim 13, wherein the third segment of the power supply line iscoupled to a starter configured to cause a restart of an engine of thevehicle, and the controller opens the first switch while the starter isdriven.